[TenTec] re: 12VDC for Peg or FD

[al_lorona at agilent.com]

> Yep, Ken tx for the pointer to the higher current boosters. 
> Good idea for 
> the EOC where we'll put an IC-706 in place. The original 706 
> we had AF 
> quality  degraded noticably below 11.5V, and it would 
> actually cut out at 
> just below 11V.  We actually have one of the N4UAU boosters on hand:

Hi, Mark,

This is a real issue with battery operation. Lead-acid batteries may start out at 12.6 V, but very rapidly the terminal voltage drops off more or less linearly with time.

I have made discharge curves for a 105 A-H lead acid deep discharge marine battery and in just a few hours of FD-type operation the voltage goes below 12.0 V. To get the full 105 A-h out of the battery, you have to accept terminal voltage of well under 11.0 V at the end of the discharge cycle. And as you point out, many radios can't tolerate this. For some radios, the receiver sound fine and there is no clue to any malfunction but the transmit signal begins to have real problems with high intermodulation products, FMing, and other crud.

Anyway, the point I want to make with you is that I have turned to putting individual nicads in series with the deep cycle battery and adding one at a time to maintain 13.8V (plus or minus) at the radio. The nicads I use are large 60 to 100 A-H cells, and at 1.3 volts each it only takes two or three to keep the total battery from dropping below 13.8 V. The reason why we do this is that many of those electronic devices that "boost" the battery voltage generate RFI themselves. There have been many posts here about switching power supplies and RFI, and these devices operate on the same principle. Be careful.

Regards,

Al  W6LX